Traditional advice says to plant tulips bulbs at a depth three times the height of the bulb -- generally about 6 to 8 inches deep. But new research from Cornell University's Flower Bulb Research Program (FBRP) has demonstrated that you can save yourself some work and still enjoy beautiful flowers without digging.
A three-year study by FBRP research director Bill Miller showed that the technique called ″top planting,″ also known as ″drop and cover,″ involved less labor and still resulted in good flowering and rebloom in succeeding years.
The cultivars 'Ad Rem' and 'Negrita' were chosen for the study because they tend to perennialze and bloom well for several seasons after planting. First the planting area was tilled to a depth of 3 to 4 inches with a rotary tiller and bulb fertilizer mixed in. Tulip bulbs were then simply placed on top of the tilled area and covered with 2-4 inches of aged mulch or well rotted compost. Miller notes that it is important to set the bulbs on the prepared soil, not press them into it, to avoid injuring the bulb base. He also cautions against over-mulching, noting that bulbs covered with 6 inches of mulch did not bloom as well by the third year as those covered more shallowly.
″Our work has shown that gardeners can enjoy masses of tulips without the work of digging a hole for each bulb,″ says Miller. ″We have had excellent return of tulips for at least three years with this method. And no digging!″
To read more about this research, go to Flower Bulb Research Program.